A recent survey of 1,000 British men has shown that a third of men aged between 35 and 60 years, are unable to see their genitals due to a protruding midriff or, less politely, a beer belly.

As a result of the survey, funded by the medical group We Love Our Health, an online men's health awareness initiative has been launched. The Big Check aims to encourage men to make a potentially lifesaving health check.

"Take off your clothes, stand upright and look down at your penis, if you can't see it, you are obese," says the group's online doctor, Johan du Plessis.

"Don't ignore it, it can knock years off your lifespan but it can also put you in serious risk from life threatening illness."

Campaign member Dr Sarah Brewer urges men to adopt a healthier life style: "Most men care more about maintaining their cars than their own bodies and often only see the doctor if told by a partner or relative."

Being overweight means that men are more likely to develop Type 2 diabetes, colon cancer, high blood pressure, high cholesterol, heart disease and other health problems.

But, what the research does not spell out is that obesity has been linked to erectile problems and difficulties with sexual performance. From a psychological point of view overweight men often feel uncomfortable with their body and have a lower self esteem.

They may suffer from anxiety, depression or emotional distress and therefore acquire performance anxiety. Unfortunately, it's not something they want to talk about, either to their GPs or a counsellor.

The social and psychological obstacles these men face are not the only factors causing sexual problems. There is also a direct biological origin. To have an erection is the result of increased blood flow in the penis and to maintain penile erection depends on a healthy circulatory system.

There has not been a similar survey in Australia or New Zealand yet, but you only need to look around to realise how many men are overweight and have a beer belly.

They don't seem to care either.

They shrug their shoulders and like to joke: "My partner likes my love handles," "I have the body of a God - and my God is Buddha." Or the best one: "I have a veranda over my toy shop."

However, overweight men should view the prospect of impotence as a compelling motivation to lead a different lifestyle; one that involves regular exercise and a healthy diet. It is for their own sakes and that of their partners.

Erectile dysfunction does not just affect overweight men. The world's largest study to examine links between erectile dysfunction and heart disease found even minor erection difficulties in healthy fit men, can be an indicator of future heart risks.

The authors of the study, undertaken in Australia and published last month in the on-line journal 'PLOS Medicine', examined data of 95,038 men aged 45 years and older.

The researchers concluded that erectile dysfunction does not cause heart disease but may be an early indicator of the problems that lead to it, such as a build-up of plaque in the arteries.

Dr Rob Grenfell, from the Australian Heart Foundation, said: "These results tell us that every man who is suffering from any degree of erectile dysfunction should be seeking medical assistance as early as possible, and also insisting on a heart check by their GP at the same time".